Vacuum circuit breakers (VCB) enable switching operation with no need for maintenance of breaker parts and thus have an increasing range of applications to railroad facilities and phase modifying facilities where frequent switching is required (see, for example, Patent Document 1 and Non-Patent Documents 1 to 3).
The switching of a capacitor bank causes, at a power-on event, a high-frequency large current about five times as high as a rated current so that roughening of electrode surface occurs by seizing associated with a preceding discharge. At a subsequent interruption event, the capacitor bank receives twice as high a voltage as a system voltage. As the withstand voltage becomes lowered due to the electrode surface roughening, there arises the problem of restriking under such a high voltage. In the case of a vacuum circuit breaker for a capacitor bank, switching operation is performed at a high frequency of about once a day. Such frequent switching operation leads to the problem of accumulation of electrode roughening by an inrush current at power-on. The vacuum circuit breaker for the capacitor bank is hence configured to ensure a high interruption speed or large gap (electrode-to-electrode distance) during interruption in order to improve withstand voltage performance between electrodes of the vacuum circuit breaker.
However, the operation force required for switching of the vacuum circuit breaker is increased as the interruption speed or interruption gap length of the vacuum circuit breaker is increased. This results in upsizing of the operation mechanism for switching of the vacuum circuit breaker.